Boreholes for hydrocarbon (oil and gas) production, as well as for other purposes, are usually drilled with a drill string that includes a tubular member (also referred to as a drilling tubular) having a drilling assembly which includes a drill bit attached to the bottom end thereof. The drill bit is rotated to shear or disintegrate material of the rock formation to drill the wellbore. The drill string often includes tools or other devices that require remote activation and deactivation during drilling operations. Such tools and devices include, among other things, reamers, stabilizers or force application members used for steering the drill bit.
Electro-mechanical control systems are often unreliable in such drilling environments. Remote control of downhole tool activation by controlling fluid pressure in the drill string often allow only a single activation/deactivation cycle, after which the control system is to be reset, while reduction in effective drill string diameter result in some systems. Utilization of the drilling fluid (e.g., mud cycled down the drill string and back up a borehole annulus) introduce the risk of inadvertent tool activation during normal drilling operations.